I know people who have done it they had some slight issues with the aftermarket parts being slightly different fit at the block end, maybe it was down to manufacturing as they wouldn't bolt straight up, they had to get a block of wood between ease them out slightly,
You may be off seeing if you can get some oem ones off a breakers or someone in eBay, at least you how they will fit straight,
As for the bits further down I think the name cars go into a y section just after the engine so you may need a bother small section to bolt it to the exhaust
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